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1. between India and Sri Lanka?
2. between Japan and continental Asia?
3. between Malaysia and Singapore?
4. between Hong Kong and Macau?
5. between Michigan and Canada?
6. between Kinshasa and Brazzaville?
7. across the strait of Gibraltar?
8. between Denmark and Sweden?
9. between Saudi-Arabia and Egypt?
10. between Alaska and Russia?
11. between Mindanao and Luzon?
12. between Honshu and Hokkaido?
13. between Ireland and Great Britain?
14. across the Bosphorus strait?
15. between Sicily and Italy?
16. across the Amazon river (without tributaries)?
(Turns out they're planning to build a bridge by 2028 but who knows)